Telephone system



y 1941- E. H. LAN HAM ETAL 2, 7,507

I TELEPHONE SYSTEM. A

Filed June 10, 1939 2 Shets-Sheet 1 M M M, W ...F

without mm m u 5. H. LAN/1AM INVENTORS L. R. 'WALLER ATTORNEY y 9 E. H.LANHAM ETAL 7,507

TELEPHONE SYSTEM Filed June 10, 1939 2 Sheets-Sheet 2 E. H. LANHAM L. R.WALLER IN VEN TORS mfTORA Ey Patented July 1, 1941 TELEPHONE SYSTEMEdward H. Lanham, Nctre Dame de Grace, Quer, Montreal, Quebec, Canbec,and Lee R. Walle ada, assignors to Western Electric Company,

Incorporated, New York, N. Y., a corporation of New York ApplicationJune 19, 1939, Serial No. 278,404

14 Claims.

'This invention relates to telephone systems and particularly tointercommunicating or conference systems involving the use ofloud-speaking and receiving equipment.

It is the object of this invention to provide an improved system oftelephone intercommunication involving a plurality of stations whichnormally have access to and are accessible from a central ofiice, suchas a private automatic exchange.

In accordance with a feature of the invention,

a system is provided in which the regular private automatic exchangefacilities are employed for the additional service of loud-speakerintercommunication.

In accordance with another feature of the m vention, an executive at aprimary station may establish connection and hold conversation with anyor all of a plurality of secondary or subordinate stationssimultaneously by dialing the code numbers of the desired secondarystations and may, at any time during an established conversation withone or more secondary stations, call in any other secondary stationswithout interference with the connections al-v ready established andwithout necessitating any operation by the subscribers whose stationsare already connected to the conference line.

A further feature of the invention resides in the use of means fordiscriminating between the use of an executive service set and a regulartelephone set at the "primary station whereby a call originated at theprimary station is automatically extended either to another station ofthe intercommunicating or conference system or to a central ofiice,depending upon which equipment is employed.

These and other features of the invention will be best understood from afollowing detailed description made with reference to the accompanyingdrawings in which:

Fig. 1 illustrates a primary station A and a plurality of secondarystations B and C each equipped with loud-speaking apparatus used inconnections established over the conference or intercommunicating lineL, and with facilities for establishing connections to a privateautomatic exchange by way of the automatic switches illustratedschematically at the right of the figure; and

Fig. 2 illustrates an automatic switch W which is controlled from theprimary station A in effecting the selective connection of any or all ofthe secondary stations to the line L and also discloses the relayequipment which funcsignals are transmitted to tions to step the switchW and to transmit call and busy signals; In reading the drawings, Fig. 2is placed immediately below Fig. 1.

Before entering into a detailed description of the operation of thesystem disclosed in the drawings, a brief reference will be made to theequipment located at each station; to the normal conditions of theseveral lines with respect to the intercommunicating or conference lineand private automatic exchange apparatus; and to the other equipmentemployed in completing conference connections and for signalingpurposes.

The primary station A is equipped with a distant talking transmitter 6!,a loud-speaker M, an amplifier 62, an executive service key Ill and anauxiliary dial I2. This equipment supplements the regular stationequipment, dia-' grammatically indicated at 63, and the dial l9. Theprimary line is normally associated with the conference line L and maybe transferred therefrom to the private automatic exchange equipment bythe operation of relay IS. The equipment at the secondary stations B andC is similar to that at the primary station except at no auxiliary dial,such as dial I2, is required. Each secondary line, or section individualthereto, terminates in contacts of the line finders Sb and Se whosecontacts are multipled with the contacts of connector switche Cb and Cc,which switches serve in completing calls incoming to the variousstations from the private automatic exchange. The transfer of thesecondary lines from their private automatic exchange switch terminalsto the intercommunleating line L is effected by the combined operationsof two relays, such as relays 46 and 50. The stepping switch W which iscontrolled from the primary station may be of any well known type andfunctions to selectively signal the various secondary stations andprepare them for connection to the line L. The actual connection of thesecondary stations to the line L is accomplished when the subscribersthereat respond to an incoming call signal. The amplifiers whichconstitute part of the substation equipments may be of any well-knowntype and are balanced to permit two-way loud-speaker conversation to becarried on freely without the necessity of operating a press-to-talkkey. Call and busy the stations under the control of vibrating reed typerelays, such as 35 and 42, which function for a predetermined intervalof time to apply a signal of correspondins duration to the calledstations.

16, being marginal, does not operate in upper V armature causes battery,upper winding of relay l3, conductor I4 of line L, back contact andinner lower armature of relay I5, winding of marginal relay [6, lowerarmatures and back contacts of relays l1 and i8, retard coil H, closedcontacts of switch Ill, pulsing contacts of dial l2, back contacts andupper armatures of relays l8 and H, pulsing contacts of th primarysubscribers regular dial l9, upper armature and back contact of relayl5, conductor 2 30f line L, to ground Relay series with thehigh-resistance retard coil H. 'Relay l3, however, does operate and inattracting its relay 21 (Fig. 2) to operate in a circuit extending fromgrounded battery, winding of relay 2|, conductor '22, left armature andback contact of relay IE, conductor2-3, to ground by way of the frontcontact and. upper armature of relay l3. At its lower armature relay l3disconnects ground from conductor 30.

by way of the lower winding of relay l3.

At its inner right armature, relay 2| con-' nects ground to conductor 24which extends to [the sleeve terminals of the switches C and S, thusmarking the primary station A busy to calls theretooriginating at orextended from the central office or privat automatic exchange A at whichthe switches are located. At its inner right armature and back contactrelay 2| opens the circuit to the lower winding of relay l5. Inattracting its outer right armature, relay 21 connects conductor 25 toconductor 26, thereby short-circuiting the winding of marginal relay "l6so that relay I3 is now held operated in a circuit which does notinclude the winding of relay IE but includes the outer right armatureand front contact of'relay 2|. The functions performed by the leftarmatures of relay 2! will appear presently.

After actuating key ll] as just described, the

subscriber at pr'imary station A manipulates "the dial 12 in accordancewith the code assigned to the secondary station B. Assuming this code tobe "3, the subscriber dials the digit 3 in the well-known manner. Relayl3, whose operating circuit includes the pulsing contacts of dial l2,followsthe dial pulses. As soon as the 'dia1-|'2 is movedoif normal, theoff-normal spring contacts 21A shunt the retard coil ll', removing itsimpedance from the pulsing loop. Relay i3 does notfcll'ow "the dialpulses even though H the retard coil is effectively shunted because thewinding' of relay I3 is short-circuited by the outer right armature andfront contact of relay 21, as hereinbefore described.

' On the first rele'se of relay l3 in response to ates "in a circuitextending'from grounded batthe actuation of dial l2, relay 28 (Fig. 2)operductor 33, lower farmature and back contact of relay 13 to ground;Relay "28 is a slow-to-release device and remains operated during thepulsing period.

Stepping magnet 3| operates in parallel with relay 28 and follows therepeated releases and operations of relay l3 caused by the manipulationof dial l2. Magnet 3| accordingly functions in a well-known manner, tostep the brushes of switch W until they engage the third contact of eachlevel. These contacts are designated on the drawings by the letters band b, respectively.

When relay 28 operated on the first-release of relay l3, it causedrelays 32 and 33 to operate in obvious circuits which include the innerright armatur and front contact of relay 28. Relay 33, in operating,locks in a circuit extending from grounded battery, its own winding andinner left armature and associated make-beforebreak contact, conductor34 to ground at the front contact and outer right armature ofslowto-release relay 32. The functions performed by the other armaturesof relays 32 and 33 will appear as the description progresses.

When the dial !2 returns to normal after the dialing of digit 3, relay28 releases due to the fact that the circuit to its winding remains openat the lower armature and back contact of relay l3. Relay 23 inrestoring its armatures opens the circuit to th winding of relay 32.This relay, being slow to release, does not immediately restore itsarmatures. Before it does So a circuit for relay 35 is completed whichextends from grounded battery, winding of relay 35, front con-- tact andleft armature of relay 32, conductor 36, left armature and back contactof relay 28, brush and contact I) of switch W, conductors 31 and 38 tothe sleeve terminals of the automatic switches Cb and Sb at the privateautomatic exchange. If the line of secondary station B is busy due to anin or out call being established over the regular private automaticexchange equipment, ground potential, in accordance with well-knownpractice, will be found on the sleeve lead. Relay 35 would thereuponoperate in the circuit just traced, before relay 32 releases itsarmatures.

Relay 35, which is of the vibrating reed type, closes an obvious circuitfor slow-to-release relay 39. Due to its vibrating characteristic, thearmature of relay 35 maintains relay 39 operated for several secondsafter the release of relay 32. In attracting its left armature,'re1ay 39establishes an obvious circuit for relay 4!). Relay Ml operates and atits right armatures and front contacts connects a busy ton signal sourceto the line L. This signal is reproduced in the loud-speaker ll atstation A to advise the calling subscriber thereat that the calledstation E is busy. The busy tone current transmitted over line L doesnot operate relay 18 at the primary station A.

If the called station B is not busied by the private automatic exchangeequipment, there will be no ground potential on'the sleeve lead .38 andconsequently relay 35 will not operate when relay 28 releases upon thecompletion of dialing.

Assuming the called station B to be idle, relay 28 releases uponcompletion of dialing, in turn releasing relay 32. Relay 32 opens thelocking circuit to relay 33, which relay, however, being slow to releasedoes not restore its armatures immediately so that a circuit is nowestablished which extends from grounded battery, winding ofslow-to-release relay 42, left armature and back contact of relay 40,front contact and right armature of relay 33, to ground by way of theback contact and outer right armature of relay 32. Relay 42 operates inthis circuit before relay 33 releases and in turn causes relay 43 tooperate in an obvious circuit. Relay 42, like relay 35, is of thevibrating reed type and due to the vibrating characteristic of itsarmature maintains relay 43 operated for several seconds after therelease of relay 33.

At its left armature and front contact relay 43 extends ground potentialover conductor 44, brush and third terminal I) of switch W, conductor45, winding of relays 46 and 41 in parallel to grounded battery. Relay41 operates and connects tone current to the called station B whichoperates the loud-speaker 48 to produce a call signal. Relay does notoperate on this tone current. When relay 42 ceases to vibrate andslow-to-release relay 43 has subsequently released its armatures, relay41 connects the tone source from the called station E and the lineconductors from station E are extended to the outer armatures of relay46.

Relay 46, which operated in parallel with relay 41, locks to ground atthe outer left armature and front contact of relay 2| by way ofconductor 49 and the inner upper armature and makebefore-break contactsof relay 46. At its inner lower armature relay 46 connects ground to thesleeve terminals of switches Sb and Cb to make the called line test busyto the regular private automatic exchange equipment. At its outer, upperand lower armatures, relay 46 transfers the tip and ring conductors ofthe called line from the private automatic exchange pares an operatingcircuit for relay 5|].

In response to the tone signal, the subscriber at station B operatesstation key 5|, thereby completing the circuit for relay 50. Thiscircuit extends from grounded battery, upper winding of relay 50, frontcontact and outer upper armature of relay 46, back contact and upperarmature of relay 41, closed contacts of dial 1|, upper armatures andback contacts of relays 12 and I6,

closed contacts of key 5|, coil 52, lower armatures I and back contactsof relays 1D and 12, lower armature and back contact of relay 41, outerlower armature and front contact of relay 46, lower winding of relay 50to ground. The impedance of coil 52 is such as not to interfere with thetransmission of speech.

Relay 50 in operating disconnects the station equivalent network 53 fromthe intercommunicating line L and connects the called station linethereto. ondary station B are thus connected together and two-wayconversation over the line L may proceed on a loud-speaker basis.

When relay 42 ceases to vibrate and releases relay 43, the rotary switchrelease circuit is closed from ground at the outer right armature andback contact of relay 26, right armature and back contactof relay 43,right armature and back contact of relay 39, outer left armature andback contact of relay 33, inner right armature and back contact of relay32, oiT-normal springs 54 of switch W, winding of release magnet 55 tobattery and ground. Release magnet 55 functions in a well-known mannerto return the switch to normal.

At the termination of subscribers at stations the primary service keyand 2| conversation between the A and B, the subscriber at stationrestores the executive II] to normal whereupon relays l3 release,allowing relay 46 to restore its releases and dis- 2 equipment and pre-The primary station A and the secarmatures and the circuit is restoredto normal.

It will be noted thatimmediately after the called station B wassignaled, the switch W was restored to normal so that it is in readinessto receive further pulses from dial I2 at station A should thesubscriber thereat desire to include other of the "secondary stations ina conference circuit. If during the conversation between the subscribersat stations A and B the subscriber at station A wishes to call in one ormore additional secondary stations for conference purposes, it is onlynecessary that the dial I2 be actuated to dial the call number ornumbers of the station or stations desired. Such operations do not, inany way, interfere with the connection already established.

Relay |3 will respond to the dial pulses in the same manner as when the"secondary station was dialed and the consequent relay operation will bethe same as already described. The switch W will, of course, bepositioned on different bank contacts in accordance with the codesdialed and will operate relays 46 and 41 corresponding to the stationscalled. In each case, switch W returns to normal after performing itsfunctions either of reporting the called line busy or operating theassociated relays 46 and 41 to prepare the called line for connection tothe common talking circuit L and to apply a tone signal to the calledline.

When the subscriber at primary station A desires an outside connection,the receiver of the regular telephone set is removed from itsswitchhook. Relay I1 thereupon operates in a circuit extending fromgrounded battery, upper winding of relay I3, conductor I4, back contactand inner lower armature of relay I 5, winding of marginal relay I6,over the closed subset loop, winding of relay I1, upper armature andback contact of relay I5, conductor 20 to ground by way of the lowerwinding of relay I3. Relay I1 operates in this circuit and disconnectsthe executive loudspeaking equipment from the line. Relay l6 alsooperates under this condition due to the absence of the high resistanceretard coil II from the circuit and in turn operates relay |5 over anobvious circuit. I

Relay I5 operated transfers the primary station A from. the line L tothe regular private automatic exchange line. At its two lower armaturesand front contacts relay 5 shunts down relay I6. Relay |.5, however, isheld operated in a circuit extending from grounded battery, lowerwinding of relay I 5, conductor 56, back contact and inner rightarmature of relay 2|, conductor 24 to ground on the sleeve terminal ofswitch S- at the exchange. It will be understood that when relay I5operated, line finder S functioned in the well-known manner to seize thecalling line and apply ground potential to the sleeve terminal thereof.

On an incoming call to the primary station from the private auto-maticexchange, relay |5 operates from ground on the sleeve circuit of theprivate automatic exchange equipment and cuts the private automaticexchange line through to the primary" station and shunts relay I6.Ringing current transmitted from the private automatic exchange operatesrelay I8 which functions to cut off the amplifier equipment at theprimary station during ringing periods. Relay I1 operates when thecalled subscriber answers the call by removing the receiver from itsswitch-hook and maintains the executive service equipment disconnectedfrom the line.

The subscribers at the secondary stations B and- C may initiate calls toand receive calls 'from the private automatic exchange in the well-knownmanner, by employing the regular telephone set. Relay 72 operates whenthe receiverat the secondary station is removed from its switchhook andcuts off the loud-speaking equipment from the line. Manipulation of thedial H causes the switches at the private automatic exchange to functionin the well-known manner to extend the connection to a called station.

What isclaimed is: 1. In a combined automatic telephone exchange andloud-speaking intercommunicating system, a primary station having aloud-speaking telephone set including a call initiating key and aregular telephone set, an intercommunicating line, a link circuitextending to automatic switches at a central office, and means fordiscriminatingbetween the use of said call initiating key and saidregular telephone set at said 7 primary station in originating a call,whereby central ofiice linkcircuit, said primary station 'beingnormallyassociated with said intercommunicating line circuit and disconnectedfrom saidoentral ofiice link circuit, switching means responsive to theuse of said regular telephone set in originating a call for transferringsaid primary station from said intercommunicating line and connecting itto said central ofiice link circuit, and means included in saidloud-speaking telephone set for rendering said switching meansinoperative when said loud-speaking telephone set is employed inoriginating a call at said station.

V 3., In a combined private automatic telephone exchange andloud-speaking interccmmunicating system, a primary station, ,aloud-speaking telephone set and a regular telephone .set at saidstation, an intercommunicating line circuit, a

-central oflice link circuit, said station being. nor- 'mally associatedwith said intercommunicating line circuit and disconnected from saidcentral office link circuit, a marginal relay included in circuitvbetween said primary station and said intercommunicating line circuit,switching means controlled thereby, means effective upon the use of saidregular telephone set in originating a call for causing the operation ofsaid marginal relay whereupon said switching means operates todisconnect said station from said intercommunicating line and connect itto said central ofiice link circuit, and means includinga key associatedwith said loud-speaking telephone set for ren- 'dering said marginalrelay unresponsive to the use of: said loud-speaking telephone set inoriginating a call at said station.

4. In a combined automatic telephone exchange and loud-speakingintercommunicating system, an intercommunicating line circuit, a stationthereon having a loud-speaking telephone set including a key and a diala central ofiice,

*to the operation of the key at "an automatic switch thereat having aterminal corresponding to said station, means responsive said stationfor applying a busy potential to said terminal, a second station, meansincluding the dial at said first station for automatically signalingsaid second station, and means operating when the subscriber at saidsecond station responds to the signal for connecting said second stationto said intercommunicating line. 7

5. In a combined automatic telephone exchange and loud-speakingintercommunicating system, an intercommunicating line circuit, a stationthereon having a loud-speaking telephone set including a key and a dial,a second station normally disconnected from said intercommunicating linecircuit, a central ofiice, automatic switches thereat having terminalscorresponding to said stations, means responsive to the operation of thekey at said first sta'tionfor applying a busy potential to the centraloffice switch terminal corresponding to said first station, meansincluding the dial at said 'firststation for automatically signalingsaid second station and applying a busy potential tothe central officeswitch terminal corresponding to said second station, and meansoperating when the subscriber at said second station responds to thesignal for connecting said second station to said intercommunicatingline,

6. In a combined automatic telephone exchange and loud-speakingintercommunicating system, an intercommunicating line circuit, a stationthereon having a loud-speaking telephone set including a key and a dial,a second station normally disconnected from said intercommunieating linecircuit, a central ofiice, automatic switches thereat having terminalscorresponding to said stations, means responsive to the operation of thekey at said'first station for applying a busy potential to'the centralofiice switch terminal corresponding to said first station, meansresponsive to the actuation of the dial at said first station subsequentto the actuation of said key for testing the central office switchterminal corresponding: to said second station, and means responsive tobusy potential encountered on the central office switch'terminalcorresponding to said second station for applying a tone signal to saidintercommunicating line, circuit. for reception by the loud-speaker atsaid first station.

7. In a combined automatic telephone exchange and loud-speakingintercommunicating system, an intercommunicating line circuit, a

station thereon having a loud-speaking telephone "set including a keyand a dial, a second station normally disconnected from saidintercommunieating line circuit, a central oiiice, automatic switchesthereat having terminals corresponding to said stations, meansresponsive to the operation of the key at said first station forapplying a busy potential to the central ofiice switch ter minalcorresponding to said first station, means responsive to the actuationof the dial at said first station subsequent to the actuation of saidkey for testing the central office switch terminal corresponding to saidsecond station, and means operating a predetermined interval of timeafter the central oiiice switch terminal corresponding to said secondstation is tested and found idle for transmitting a tone signal to saidsecond station.

8. In a combined automatic telephone exchange and loud-speakingintercommunicating system, anintercommunicating line circuit, a stationthereon having a loud-speaking telephone set including a key and a diaLasecond station normally disconnected from said intercommunieating linecircuit and having a loud-speaking telephone set including a key, acentral office, automatic switches thereat having terminals corsecondstation for reception by the loud-speaker thereat.

9. In a combined automatic telephone exchange and loud-speakingintercommunicating station responds to the signal for connecting saidsecond station to said intercommunicating line.

10. In a combined automatic telephone exchange loud-speakingintercommunicating system, an intercommunicating line circuit, astanection for disconnecting said loud-speaking telephone set from 12.In a combined automatic telephone exchange and loud-speakingintercommunication pleting the connection of the called line to theintercommunicating line.

. In a telephone conference system, a called 13 station, a callingstation, a line circuit normally said automatic switch. 14. In atelephone conference system, a calling station, a plurality of calledstations, a line cirthereof to said line independent of said automaticswitch, and means operating at the expiration of the predeterminedinterval of time during which tli called station is being signaled forreleasihg said automatic switch-whereupon sa-i-d automatic switchbecomes available for further control by connecfiion to said li'ne'without distufloing the connection of said-one o said line.

f said called stations with LEE R. WALLER.

